The determination of the ultra-wideband and time-domain behavior of open area test sites using frequency domain measurements and the complex antenna factor concept

The ultra-wideband and time-domain characteristics of representative Open Area Test Sites (OATS) are determined numerically and experimentally. The analysis and measurements are performed in the frequency domain over a very wide bandwidth (several decades) using a set of calculable biconical antenna with known complex antenna factors (CAFs) according to S. Ishigami et al. (1996) and J. McLean et al. (2002). The principal advantage of the biconical antennas over typical UWB antennas, such as TEM horns, is that their radiation pattern including phase information is well-behaved and numerically calculable. The minimum scattering features of the radiation patterns of the calculable biconical antennas are crucial to correctly quantifying the reflection characteristics of an OATS. The normalized complex site transfer function according to J. McLea et al. (2002) is derived from complex 2-port measurements made with pairs of such antennas and an automatic vector network analyzer can then be used to derive the time-domain characteristics, e.g. the impulse response, of the site via Fourier transform techniques. Numerical simulations and experimental characterization of the time-domain response of representative OATs will be presented highlighting the non-ideal behavior of such sites including ground plane edge reflection/diffraction and imperfect specular reflection.